The 37 S precursor to ribosomal RNA is the primary transcript of ribosomal RNA genes in Saccharomyces cerevisiae

The primary precursor to ribosomal RNA, identified by pulse-chase and fingerprint analyses, was isolated from lysates of an osmotic-sensitive Saccharomyces cerevisiae mutant. This precursor rRNA molecule has an electrophoretic mobility oorresponding to 37 S RNA and an estimated molecular weight of about 2.8 × 106.